1. Field of the Invention
The present invention relates to a fuel vapor recovery apparatus.
2. Description of the Related Art
In order to facilitate level shifts of the fuel liquid surface in a fuel tank in accordance with changes in the amount of fuel present in the fuel tank, there is a need to open the internal space of the fuel tank to the atmosphere. However, since fuel vapor normally occurs in fuel tanks, a fuel tank connected in open communication to the atmosphere allows fuel vapor to be easily emitted into the atmosphere. To solve this problem, Japanese Patent Application Laid-Open No. HEI 8-197968 proposes an apparatus in which a canister for adsorbing fuel vapor from a fuel tank is provided in a communication path between the fuel tank and the atmosphere.
The amount of fuel vapor that such a canister is able to adsorb is limited. If the fuel vapor adsorption limit is exceeded, fuel vapor passes through the canister and flows out into the atmosphere.
Therefore, the aforementioned laid-open application (HEI 8-197968) proposes a construction in which the canister is connected to an intake passage of an internal combustion engine. During operation of the engine, fuel vapor is released from the canister into the engine intake passage so that the fuel vapor adsorption limit of the canister will not be exceeded.
However, if a large amount of fuel vapor is generated in the fuel tank, or if fuel vapor adsorbed by the canister is not released into the internal combustion engine for a long time, fuel vapor passes through the canister and flows out into the atmosphere.